90 Rockwell Automation Publication 1412-UM001D-EN-P - September 2012
Appendix C Mathematical Formulas For Various Parameters
Total active energy consumed:
Wh[1][3] = Wh[1][0] + Wh[1][1] + Wh[1][2]
Total apparent energy consumed:
VAh[1][3] = VAh[1][0] + VAh[1][1] + VAh[1][2]
Total reactive capacitive energy consumed:
VARhC[1][3] = VARhC[1][0] + VARhC[1][1] + VARhC[1][2]
Total reactive inductive energy consumed:
VARhL[1][3] = VARhL[1][0] + VARhL[1][1] + VARhL[1][2]
Hysteresis
Hysteresis is a filtering principle, often used after the threshold detection has
occurred. A correct setting of hysteresis value will avoid repeated triggering when
the measure is varying close to the threshold.
The event detection is activated when the measure is going over the threshold but
it can only be deactivated if the measure goes under the threshold minus the value
of the hysteresis.
The default hysteresis value is 2% of the reference voltage but it may be set in the
range of (1%, 5%) depending on the voltage stability of the system.
Swell Detection
Wh
[
1
][
i
]
=
Active energy consumed phase i + 1
W[i]
3600
∑
Tint
VAh
[
1
][
i
]
=
Active energy consumed phase i + 1
VA[i]
3600
∑
Tint
VARhL
[
1
][
i
]
=
for VAR[i] ≤0
Reactive inductive energy consumed phase i + 1
–VAR[i]
3600
∑
Tint
VARhC
[
1
][
i
]
=
for VAR[i] ≥0
Reactive capacitive energy consumed phase i + 1
VAR[i]
3600
∑
Tint
Hysteresis =
2% Uref
Swell duration
Threshold of swell =
100% Uref
Level to go back =
100% - 2% = 98% Ure
